233 



Guppy Reprint 



75 



Page 92 



posteriorly high with a decided obtuse angle formed by a 

 low keel running from the umbo, on the upper and posterior 

 side of which keel the shell is covered with a black 

 epidermis. Valves flattened, white, rather fragile, marked 

 with concentric striae of growth, which are worn smooth 

 on the disk and umbones, but towards the ventral margin 

 are covered with a yellowish brown wrinkled epidermis. 

 Length 85, height 60, thickness 30 mm. 



The details of the hinge are somewhat similar to those 

 of the hinge of Hcmimacti a g-igantea , but the pcstcaidinal 

 area resembles that of Schizodesma. The latter feature is 

 much developed in our shell, and is remarkable for its 

 black epidermis, that of the other portions of the shell being 

 of a light brown. M. anserina may possibly be allied to the 

 M. similis of Gray in Beechey's Voyage, an Australian 

 shell, (not the M. similis of Say — ovalis Gould, which is an 

 inhabitant of North America.) 



Explanation of Plate III. 

 All the figures are of the natural size. 



Fig. 1. Mactra anserina, right valve — Cumana, Venezuela. 

 " 2. Ve?ius superba, right valve 



' ' 3. Cardium eburniferum, right valve - S. Coast, Trinidad 

 " 4a Area centrota, right valve, interior. 

 " 4b " " right valve of a large specimen, 



[exterior. 



The last two species were described in the Proceedings 

 of the Scientific Association of Trinidad, vol. i, 1869, pp. 

 367-368. Area centrota had been previously described as 

 a fossil at p. 175 of the same vol. (1867). 



